Aluminum alloys have excellent mechanical properties, physical and chemical and technological properties and therefore found application in the automotive, aerospace, chemical and food industry, but also in electrical engineering. They have been used in the automotive industry because of their low density, which reduce the mass of cars and contributes to the reduction of fuel consumption, thereby directly reducing CO2 emissions. One of the most commonly used alloys in the automotive industry is AlSi7Mg0,3 alloy. The alloy has been poured into die which ensures optimal cooling and solidification conditions and better mechanical properties were achieved. Considering casting geometry, casting is poured by gravity tilt casting technology. Within this paper, has been shown that different cooling speed as well as pouring rates can affect development of casting microstructure and mechanical properties. Metallographic examination reveals primary αAl dendrites and eutectics (αAl + βSi) and other intermetallic phases based on Fe and Mg. In this paper the influence of three sets of parameters was investigated on microstructure development and development of αAl in correlation with wall thickness: I) optimal casting parameters with applied cooling casting die, II) casting parameters without cooling and III) casting parameters with faster pouring rate. A positive impact of increased cooling rate and solidification rate on refinement of microstructural constituents first of all at αAl till 25 mm of wall thicknesses. Mechanical testing revealed difference in tensile strength and elongation values for case I, II, and III. In first case with optimal parameters, the best mechanical properties are obtained. Lower mechanical properties caused by defects in casting were determinate by fractography analysis. In order to determine the cause of the defects, a numerical simulation of the casting was carried. Defects occurred in castings were determinated as shrinkage porosity and unidirectional solidification in hot spots.